Developmental dyslexia is a specific learning disability characterized by difficulty in learning to read. Some dyslexics also may have difficulty learning to write, to spell, and to speak or work with numbers. Some researchers estimate that as many as 15 percent of American students may be classified as dyslexic. Children with dyslexia are not all alike--the only trait they share is that they read at levels significantly lower than is typical for children of their age and intelligence. Most experts agree that a number of factors probably work in combination to produce this disorder; possible causes of dyslexia may be grouped under three broad categories: educational, psychological, and biological. Educational causes may include teaching methods, the nature of the English language, and interpretation of intelligence tests. The usual treatment for dyslexic students is to modify teaching methods and the educational environment based on the specific learning problems of the individual dyslexic student. The prognosis for dyslexic students is mixed because there is a wide diversity of symptoms and degrees of severity. However, it is clear that an effective remedial program is very crucial and that early diagnosis and treatment are essential. (CB)